1. Field of the Invention
The invention relates to a computer key, more particularly to a computer key which includes a biasing member mounted between a base member and a push button such that the biasing member will not disengage from the base member regardless of the position of the applied force. The base member is of a unique structure such that the overall height of the computer key is reduced as compared to that of the conventional computer key.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a known computer key is shown to include a base board consisting of a lower base plate 16 and a membrane circuit 15, an upper base plate 12, an upright elastomeric biasing member 14, first and second linking frames 131, 132, and a push button 11.
As illustrated, the membrane circuit 15 is disposed above the lower base plate 16. The upper base plate 12 is disposed above the membrane circuit 15 and includes a hole defining portion 12A with an inner peripheral portion 12B that defines a retaining hole 21 therethrough to expose a contact area 150 of the membrane circuit 15, a first hingeably retaining groove 122, and a first slidably retaining guideway 123 disposed on an opposite side of the retaining hole 21 relative to the first hingeably retaining groove 122. The inner peripheral portion 12B has an upper annular wall 22 with a first inner diameter, and a lower annular wall 23 with a second inner diameter which is greater than the first inner diameter to form an annular shoulder 24 between the upper and lower annular walls 22, 23.
The biasing member 14 includes an upper depressing portion 142, and a spacing lower portion 141 to space the upper depressing portion 142 from the contact area 150. The lower portion 141 of the biasing member 14 has a flange portion 32 which extends outwardly from a lower end thereof and which is inserted into an annular groove defined by the shoulder 24 and the membrane circuit 15. The depressing portion 141 of the biasing member 14 is movable against the biasing action thereof and through the retaining hole 21 to depress the contact area 150 of the membrane circuit 15 for generation of an electrical signal.
The push button 11 is disposed to actuate the the biasing member 14, and has a second hingeably retaining groove 112 and a second slidably retaining guideway 113 which are disposed underside thereof in diagonal positions relative to the first slidably retaining guideway 123 and the first hingeably retaining groove 122, respectively.
The first linking frame 131 includes a first transverse axle 1311 press-fitted to and retained hingeably in the first hingeably retaining groove 122 of the upper base plate 12, and a pair of first linking arms 1312 which extend respectively and radially from two ends of the first transverse axle 1311 and which have a pair of first hooking fingers 1313 at distal ends thereof and parallel to the first transverse axle 1311. The first hooking fingers 1313 are fitted to and slidably retained in the second slidably retaining guideway 113 of the push button 11.
The second linking frame 132 includes a second transverse axle 1321 press-fitted to and hingeably retained in the second hingeably retaining groove 112 of the push button 11, and a pair of second linking arms 1322 which extend respectively and radially from two ends of the second transverse axle 1321 to flank the first linking arms 1312 and which have a pair of second hooking fingers 1323 at distal ends thereof parallel to the second transverse axle 1321. The second hooking fingers 1323 are fitted to and retained slidably in the first slidably retaining guideway 123 of the upper base plate 12. The first and second linking arms 1312, 1322 are connected pivotally at intermediate portions thereof to confine a column of space for accommodating the depressing movement of the biasing member 14 when the first transverse axle 1311, the first hooking fingers 1313, the second transverse axle 1321, and the second hooking fingers 1323 are received in the first hingeably retaining groove 122, the second slidably retaining guideway 113, the second hingeably retaining groove 112 and the first slidably retaining guideway 123, respectively.
A drawback of the aforesaid computer key resides in that the upper base plate 12 must have a relative thickness in order to form the annular shoulder 24 between the upper and lower walls 22, 23. As a result, overall height reduction thereof is still not satisfactory.